1. Field of the Invention
The present invention relates to a belt supporting device, and an automatic document feeding apparatus and a document reading apparatus using the device.
2. Description of the Related Art
Conventional switching of two members for supporting a belt between a positioned state and a non-positioned state by a simple method, for example, in an automatic document feeding apparatus will now be described with reference to FIG. 7.
FIG. 7 illustrates an automatic document feeding apparatus and an image forming apparatus. In FIG. 7, the automatic document feeding apparatus is divided along two dot chain lines into a document supply section A and a belt conveyor section B. A copying machine body C serving as the image forming apparatus reads a document D laid on a platen (document reading section) 110 by reading means (not shown), forms a toner image to be a transfer image on a photoconductive drum (image forming means) 100, and transfers the transfer image onto a conveyed sheet S, thereby forming an image on the sheet S.
First, the construction of the document supply section A will be described.
A plurality of documents D stacked on a document tray (document holding means) 102 are sequentially delivered from the lowermost one by a semicircular roller 104, separated one by one by a comb-like separating and nipping portion composed of a delivery roller (document feeding means) 103 and a separation belt 106, and conveyed to register rollers 107 and 108a, where the document D is registered at its leading end and then conveyed to the belt conveyor section B with a predetermined timing.
The belt conveyor section B is a mechanism that conveys the document D over the platen 110 while pressing a document conveyor belt 116, which is coated with urethane rubber and stretched between a driving roller 111 and a driven roller 112, against the platen 110 by presser rollers 113, 114, and 115.
The document D conveyed from the document supply section A is further conveyed by the document conveyor belt 116, and stopped at a predetermined position on the platen 110. Then, a transfer image corresponding to a document image on the document D is formed on the photoconductive drum 100 in the copying machine body C, transferred onto the sheet S, and fixed by a fixing device (not shown), thereby forming an image on the sheet S.
After that, the document D is conveyed by the document conveyor belt 116 in an opposite direction (to the left in FIG. 7), ejected by eject rollers 108b and 109b, and returned again to the document tray 102.
The automatic document feeding apparatus having the construction described above has a problem in that the document conveyor belt 116 can be soiled. Toner and pencil lead powders on the document D can transfer onto the document conveyor belt 116 owing to the rubbing of the document D and the document conveyor belt 116, thereby soiling the document conveyor belt 116. This soil can also be copied as images outside an image area and may be found in a copy image, which degrades the quality of print on a copy sheet.
As one measure of solving the above problem, the document conveyor belt 116 is regarded as a part that needs to be periodically replaced, and is replaced with a new belt on the market as needed, while there is a demand for an easier operation of replacing the document conveyor belt 116. Accordingly, a unit-combined structure shown in FIGS. 8 and 9 is adopted to reduce the replacement time.
FIG. 8 is a front view of an automatic document feeding apparatus utilizing the unit-combined structure, and FIG. 9 is a side view showing a stay structure of the automatic document feeding apparatus.
A document supply section A and a belt conveyor section B are fixed to a bottom plate 154 and a coupling plate 153 attached thereto by screws on the rear side of the apparatus. On the front side of the apparatus, the document supply section A is positioned with burrs 150a and 150b of its front plate 150 engaged with a coupling plate 151, and is fixed by three screws 160.
The belt conveyor section B is also positioned with burrs 152a and 152b of its front plate 152 engaged with the coupling plate 151, and is fixed by a screw 161. A supporting member 156 for supporting a driven roller 112 generates tension for tightly stretching a document conveyor belt 116 by using a tension spring 157.
In replacing the document conveyor belt 116, the tension spring 157 is first removed, and the supporting member 156 is moved leftward in FIG. 7. Then, the four screws are removed, the coupling plate 151 is detached, and a space is thereby formed between the document supply section A and the belt conveyor section B. Through the space, the document conveyor belt 116 is drawn forward.
In the related art described above, however, there is a need to fix the coupling plate 151 by the plural screws 160 and 161 and to fit all the plural burrs 150a, 150b, 152a, and 152b in order to position the coupling plate 151. Therefore, a certain degree of technique is required and a screwdriver is indispensable as a tool, which leads to the following problems:
1) It takes much time to detach the coupling plate 151.
2) Since only a serviceperson can perform the belt replacement, when a user needs to perform replacement, it is difficult to respond quickly to the need.